1. Field of the Invention
This invention relates to an improvement in a process for the removal of solid fines from a gaseous mixture containing the same.
2. Description of Information Disclosures
It is known to remove solids present in a gaseous stream by contacting the gaseous stream with finely divided contact solids. Such gas-solids separation processes are sometimes referred to as granular bed filter processes, see, for example, Perry's Chemical Engineers' Handbook, 4th Edition, McGraw Hill at 20-74 and 20-75. Furthermore, the contact particles in the separation processes may be subjected to electrostatic forces to increase the efficiency of the separation. See, for example, U.S. Pat. Nos. 4,126,435 and 4,017,278, the teachings of which are hereby incorporated by reference and UK patent application GB No. 2,036,604A.
In the separation processes such as the electrofiltration processes described in the above mentioned patents, an electrically conductive member is disposed within a moving mass of substantially electrically resistive solid contact particles. A voltage is applied to the electrically conductive member during the contacting of the gas containing finely divided solids with the mass of solid contact particles. The electrically enhanced granular filtering stage is effective to remove the major portion (e.g. 99%) of fines from the gas being treated. A remaining portion of the fines (e.g. 1%) may still be in the gaseous effluent of the electrically enhanced granular filtration zone. When the fines that remain in the gaseous effluent are electrically conductive, for example, coke particles, the fines recovered from the gaseous effluent cannot be recycled to the electrically enhanced filtration zone since they would build up to a level so as to affect the operation of the process.
It has now been found that the electrical conductivity of coke fines can be decreased so that they may be recycled to the electrically enhanced granular filtration zone and that the granular filtration stage itself is also improved.
It is known that solids can be separated from a liquid medium by use of flocculating agents such as polymers. Flocculating agents are commercially available.
U.S. Pat. No. 4,256,468 discloses a method for removing particulates and condensable matter from a sinter plant gas. An anionic polymer flocculating agent is added to a water slurry and the flocculated solids are separated from the water.
U.S. Pat. No. 2,894,603 discloses treating a water and soot slurry with a flocculating agent and separating the soot from the water in a filter.